First an aside on the backstop. Corbyn is entirely right that it can't be ended unilaterally, but I really don't know what people expected. There has to be a backstop for there to be a Withdrawal Agreement, as the future relationship will be negotiated after Brexit. 2/ pic.twitter.com/gRP2MsvvFz

Even if you are planning a future relationship that would mean an invisible border in Northern Ireand, there's no guarantee that there'll be an agreement. A backstop is for then, and if it can be unilaterally ended, it's not a Backstop. 3/